Elemental (pure) fluorine is the, or close to the, most reactive substance known to man. Almost anything placed in the path of a stream of fluorine gas will spontaneously burst into flame. This includes things like, oh, say glass, steel, and other things not normally thought of as flammable. It is, therefore, fairly difficult to have a sample of it in an element collection. I used to have a statement here that there was no transparent container that could hold fluorine for any length of time, but I was corrected by a man who has figured out how to do it. See the thin tube below to see how it's done.

The video for the first sample below is one made in the lab of Tryggvi Emilsson at the University of Illinois in the 1980s. Many other segments showing fluorine reacting with other substances were made, but appear to have been lost. (If you know of a copy of these videos please let me know!)

It might seem paradoxical that many compounds containing fluorine are extremely non-reactive, but actually this is two sides of the same coin. Fluorine is very reactive because it likes to bond very strongly with other atoms: Once that violent reaction has taken place, the fluorine is not about to let go again.

The best known non-reactive fluorine compound is Teflon, discovered by accident and now used everywhere for its slipperiness and inertness, and which I use as my first fluorine sample.

When you screw together cast iron water or gas line pipe, you have to put thread seal compound or tape on the threads first, or else it will leak. The most popular choice is PTFE (polytetrafluoroethylene, otherwise known as Teflon) tape, which is a soft, stretchable material that is very slippery and very resistant to chemical attack. This particular roll is pink, which is not characteristic of Teflon, it's a dye added to indicate that this is thicker-than-usual tape.

Amazingly, on a weight-for-weight basis this tape is over 75% fluorine (the other 25% is carbon). Since pure fluorine is violently, explosively dangerous and extremely difficult to store, this was my best fluorine sample for a long time (see below for some real elemental fluorine).

PTFE tape is also a curious demonstration of the power of convention. It always comes on a particular kind of plastic spool, with a particular kind of snap-on cover to keep it clean. Every brand, every manufacturer, every store you look in, it's always exactly the same type of container. It would be fascinating to know the story of how this came about, but at this point the convention is so strong that if any manufacturer tried to sell Teflon tape in a different package, they probably wouldn't sell more than a roll or two. Those would be returned as purchasing errors, because anyone who is looking for Teflon tape will be looking for a particular shape of package, and won't even see any that's the wrong shape.Source:Hardware StoreContributor:Theodore GrayAcquired:15 April, 2002Text Updated:20 November, 2008Price: $2Size: 2"Purity: 75%

Freon-22.
Freon-22 is Chlorodifluoromethane, or CHClF2. Not quite as much fluorine as Teflon, but still quite a bit of it. This sample isn't exactly in the table, but it's over the table, in the air-conditioning system on the roof of our building.Source:Ed Pegg JrContributor:Ed Pegg JrAcquired:11 September, 2002Text Updated:20 November, 2008Price: $0Size: 18"Purity: 44%

Sample from the RGB Set.
The Red Green and Blue company in England sells a very nice element collection in several versions. Max Whitby, the director of the company, very kindly donated a complete set to the periodic table table.

Almost all the samples in the set are very, very nice, but this one I have to tease a little bit. No doubt the glass ampule did at one time contain elemental fluorine: You can tell because it ate the glass on its way out. Glass will actually burn in a stream of pure fluorine (video coming soon). So there may be some silicon fluoride lining the inside of the glass, but there is virtually no chance that there is any element fluorine still inside.

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

This sample is not marked as being a dummy (as the radioactive ones in the set are), but it obviously is. Elemental fluorine cannot be contained in ordinary glass: It eats the glass. Although it's possible to store fluorine in special containers (see the next sample) it's quite obvious that this is not such a container.

Real visible fluorine.
I used to think that there was no known transparent container that could contain fluorine without getting eaten by it. Then I got this email:

Now, respectfully, I must take up a little bit of a qualm with your claim in fluorine...You mention that "There is no transparent container that will hold it." Granted that is true if you're talking a "forever" time scale, but I strongly believe on a "realistic" scale (a few decades) it can be done...albeit with some difficulty and great time placed into it. The way best to do it is first to get yourself a pure, single-crystal quartz tube...Now that means one with an extremely high amount of surface Si-O-Si bonds and VERY few Si-OH endcaps. The best way to do this is to take the inside portion of the quartz tube and silylate it. Then anneal it at the highest possible temperature that your annealing oven can stand...This will drive off essentially ALLLLLLL the Si-OH end caps. Because remember, the real killer in fluorine gas for Si-O's is not the fluorine, but the OH's and their ability to start a chain reaction with small amounts of HF in the fluorine gas. So, the first thing you need to do is get rid of the Si-OH's which that should take care of as best as possible. Now, being absolutely certain that your quartz tube is flamed and ultra-dry, there's another step...There was a fluorocarbon grease that DuPont made many years ago that was ultra-high-purity completely fluorinated, medium-high mol.weight fluorocarbon grease (like a lower-molecular weight Teflon)...Take that stuff and literally melt it into the tube...It's clear and translucent and won't affect the optics after the next step...So then take a high temperature vacuum oven and turn the tube upside down and melt the grease back out...What this does is leave a verrrrry thin, essentially invisible layer of fluorocarbon grease layer on the inside of the tube. This layer acts as a secondary "buffer" layer to the quartz. So IF there are any Si-OH's left on your quartz, they are difficult to get at by the fluorine gas because the fluorine gas has a difficult time penetrating the grease...This step will add years to your fluorine gas display. Then the more difficult thing to do is to make sure the quartz tube has a high-purity Teflon screw-top stopper to it so that it can seal ultra-tightly. (again, pure fluorine gas without any water/HF in it may "trade" fluorines with Teflon, but you still have Teflon; same goes for the grease, the grease may "trade" fluorines as we've seen in some isotopic studies, but it remains a carbon-fluorine bond).
Then you should get a sacrificial vacuum line (kind of expensive, but it'll just be fogged up after you're done though it's best to throw it away because the integrity will be damaged) and run your fluorine gas THROUGH A LIQUID NITROGEN FILLED TRAP into your evacuated quartz tube. This is the most important AND DANGEROUS step. This step is the most important because ALLLLL commercial fluorine sources have either water or HF in them. The water and HF are what will start the "chain reaction" of eating away at things. And all it takes are a few atoms of these to get it started...But the N2(l) will definitely remove ALL of them...But the fluorine gas will still have a small amount of volatility to it so as to fill your quartz tube with approximately a quarter-atmosphere of pure F2. Now if you do anything with fluorine and leave ANY HF or H2O in it, fuggetaboutit...You'll get your stuff eaten away promptly. You won't get a full atmosphere of fluorine in your quartz sample tube like I said, but it will be enough to see under the right light and circumstances. And 50 years from now those one or two atoms of HF and H2O that are left in there will eventually have done enough damage to destroy your sample tube, but I don't plan on worrying about it 50 years from now.
Sorry if that bored you...But I do say it with utmost respect...I spent 10 years fiddling and trying to perfect the best way to get a fluorine sample, and that's the best way I could get it...So, methinks there are ways to store fluorine safely in a visible specimen tube; it just takes a great amount of patience, diligence, safety-thoughts and equipment.

I stand corrected! Not only that, he actually sent me one, it's beautiful, and just for good measure it's the 500th element sample added to my collection. He'll even make you one, if you're willing to pay the price, and based on the description above I'm sure you won't mind paying him the very reasonable couple of hundred dollars he asks. Click the Source link for more information and a link to his eBay auctions.Source:Greg PContributor:Greg PAcquired:18 April, 2003Text Updated:20 November, 2008Price: DonatedSize: 7"Purity: >99%

Teflon coated frying pan.
Teflon is a popular stick-resistant coating for pans, because it's resistant to heat and sticking. (The purity figure refers to the percentage of fluorine in pure Teflon.)Source:WalmartContributor:Theodore GrayAcquired:8 February, 2009Text Updated:8 February, 2009Price: $8Size: 8"Purity: 76%

Gore-Tex fabric.
Gore-Tex is a brand name of an expanded polytetrafluoroethylene material. (The raw material is commonly known as Teflon, another brand name in principle, but one that has become essentially generic.) Gore-Text fabrics are used in clothes because it allows water vapor to pass through while blocking liquid water. Thus you can sweat though it in the rain without getting wet. Isn't modern technology wonderful? The white back side of this fabric is the Gore-Tex liner, the purple front is some other material.
(The purity figure refers to the percentage of fluorine in pure Teflon.)Source:eBay seller fabriclauncherContributor:Theodore GrayAcquired:8 February, 2009Text Updated:8 February, 2009Price: $7Size: 8"Purity: 76%

Gore-Tex filter.
The name Gore-Tex is best known for its use in clothing, but there are many technical and medical applications for this Teflon-based fabric as well. This rather large filter bag is one, though I have no idea what it is meant to filter.
(The purity figure refers to the percentage of fluorine in pure Teflon.)Source:eBay seller fabriclauncherContributor:Theodore GrayAcquired:8 February, 2009Text Updated:8 February, 2009Price: $7Size: 48"Purity: 76%

HUGE cylinder of Teflon.
This is a marvelously huge cylinder of pure solid slick-as-ice Teflon. It's surprisingly heavy: Unlike most plastics, which are typically lighter than water, Teflon is more than twice the density of water. Teflon is very useful stuff because almost nothing sticks to it, and it's impervious to most chemicals. But for purposes of element collecting its main value is that it packs a remarkably high percentage of fluorine into a small space. By weight, Teflon (polytetrafluoroethylene) is nearly 76% fluorine (the remainder being carbon). There are two fluorine atoms for every carbon atom, and each fluorine atom weighs more than the carbon atom.
This 31-pound cylinder thus contains about 23.5 pounds of fluorine and only 7.5 pounds of carbon, which makes it by far the largest raw quantity of fluorine in my collection. Of course it's not pure fluorine, and the properties of Teflon in no way resemble the properties of fluorine gas, but still, it's a heck of a lot of the element.Source:eBay seller rdr-electronicsContributor:Theodore GrayAcquired:8 February, 2009Text Updated:10 February, 2009Price: $100Size: 12"Purity: 76%

Fluoride toothpaste.
The use of fluoride ions in toothpaste is nearly universal. This brand is not special in containing about 0.1% by weight of fluorine atoms (added in the form of sodium fluoride). Its main distinguishing feature is that it came in a more attractive box than most.Source:WalmartContributor:Theodore GrayAcquired:8 February, 2009Text Updated:8 February, 2009Price: $4Size: 6"Purity: 0.1%

Fluoridated bottled water.
Some people buy non-fluoridated bottled water because they think the near universal fluoridation of municipal water supplies is a plot by the government. And indeed they are right, it may well be a plot by the government to, oh, I don't know, prevent tooth decay?
Other people, for example those whose drinking water comes from a private well and thus is not fluoridated, buy special bottled water like this so they or their children can enjoy the benefits of fluoridated water, which may or may not include mind control by the black helicopters.Source:WalmartContributor:Theodore GrayAcquired:28 February, 2009Text Updated:1 March, 2009Price: $3Size: 10"Purity: 0.0001%

Gore-Tex suture.
This is lovely Gore-Tex (Teflon) surgical suture, with single-use needle attached. It came packaged very elaborately so you could pull it out and use it immediately without any danger of it tangling. Source:eBay seller camsurgContributor:Theodore GrayAcquired:11 March, 2009Text Updated:17 March, 2009Price: $30Size: 1"Purity: 76%

Banded Fluorite, Sierra County, New Mexico
This specimen was found in the steep section of tailings of an abandoned mine. Also included with some specimens are quartz, barite, granite and/or jasper. It fluoresces a nice vibrant purplish blue in both short & long wave ultra-violet light.

Fluorite Crystals, Kendall Mtn. near Silverton, San Juan County, Colorado.
This specimen was found in the steep section of tailings of an abandoned mine. These crystals fluoresce a nice vibrant powder blue or purplish blue in ultra-violet light.

Very large fluorite. (External Sample)
This is a huge, flat slab of fluorite crystals from the (now closed) mines in Southern Illinois. It is illuminated from the opposite side to show the translucence of the crystals.Location:John Gray's CollectionPhotographed:3 December, 2004Size: 24"Composition:CaF2

Fluorite.
This crystal is one I bought years ago but only recently found in a box. It's probably from southern Illinois but I don't really know, having long ago lost the tags.Source:Theodore GrayContributor:Theodore GrayAcquired:15 January, 2005Price: UnknownSize: 6"Composition:CaF2

Fluorite.
This crystal is one I bought years ago but only recently found in a box. It's probably from southern Illinois but I don't really know, having long ago lost the tags.Source:Theodore GrayContributor:Theodore GrayAcquired:15 January, 2005Price: UnknownSize: 5"Composition:CaF2

RbMnF3 crystal.
I don't even know what you'd call this other than by its chemical name: It's a pretty pinkish little bar of what is probably a single crystal, crudely cut and roughly surfaced, but not polished to any significant degree. It came from a batch of old samples and research materials being discarded by Ethan's university. The fact that it's translucent and colored makes me think it might be intended as some kind of laser material, whether it worked or not I have no idea. The fact that they threw it away may or may not indicate something about its usefulness.Source:Ethan CurrensContributor:Ethan CurrensAcquired:16 March, 2007Text Updated:14 October, 2008Price: DonatedSize: 1"Composition:RbMnF3

Halothane vaporizer.
Halothane is C2HBrClF3, basically a chlorofluorocarbon of the ozone-depleting variety. But surprisingly, it's also a very widely used surgical anesthetic. This vaporizer is used for administering the gas to patients and has controls for carefully adjusting the dose.Source:eBay seller i_sell_techContributor:Theodore GrayAcquired:28 February, 2009Text Updated:1 March, 2009Price: $100Size: 8"Composition:C2HBrClF3

Mica sheet.
This is a sheet of mica, a papery thin mineral that was often used as an electrical insulator. The term mica refers to a range of specific minerals and I don't know which one this is exactly, so the composition is just a guess.Source:Mark PetersonContributor:Mark PetersonAcquired:13 January, 2010Text Updated:13 January, 2010Price: DonatedSize: 3"Composition: (KLi2Al(Al,Si)3O10(F,OH)2